I've got a spreadsheet that is getting new entries posted to it. I want to
know if a the same person with the same dollar amount has already been
entered before. The problem is that the MATCH formula is matching the line
with itself if it doesn't find a prior match. Is there any way to have the
match stop at the row just prior to the one being entered? (Without the user
having to maintain the formula)
Ex:

{=MATCH(A4&B4,$A:$A&$B:$B,0)}

NAME $$ Matched Row
joe 20 1 {=MATCH(A1&B1,$A:$A&$B:$B,0)}
sam 15 2 {=MATCH(A2&B2,$A:$A&$B:$B,0)}
ralph 50 3 {=MATCH(A3&B3,$A:$A&$B:$B,0)}
joe 20 1 {=MATCH(A4&B4,$A:$A&$B:$B,0)}